Construction workers not only have higher rates of work-related injuries than other trade groups but they are also among the most likely workers to experience serious occupational injuries. Fatal and lost work time injuries continue to rank among the highest in the U.S., and national rates of disabling injuries have risen in the construction trades in recent decades which is of great concern from human and economic perspectives. The objectives of the project are to test the utility and feasibility of active injury investigations in identifying causes of work-related injury among a large cohort of residential and drywall carpenters, known high risk groups within the construction industry. Additionally, specific risk factors for occupational back disorders that result in prolonged loss of time from work will be explored with a case-control design which uses data gathered prospectively through reporting and investigation. The specific aims of the project include the following: (1) Identify a cohort of drywall and residential carpenters to participate in a prospective study of the etiology of workplace injuries; (2) Develop methods for the prospective reporting of injuries, the systematic collection of data from injury investigations, and analyses of both coded and descriptive data; (3) Conduct both rate-based and case-based analyses of injuries among the defined cohort of drywall and residential carpenters. These analyses have the specific objective of identifying high risk groups and causes of injuries; and (4) Demonstrate the use of these prospectively collected data in exploring risk factors for prolonged loss of time from work following back injury using a case-control design.